The aim of this study is to elucidate the structure and function of relaxin with special emphasis on the human hormone. The structure of the porcine hormone is now known and the human hormone structure can be obtained by comparative studies. Some effort will be made to obtain and sequence the prohormones of relaxin. Evolutionary relationships between relaxin and insulin will be traced by examining relaxin obtained from primitive species. In addition the effect of relaxin on its target organs with respect to macromolecular metabolism will be examined.